It is standard practice for official seals, tags, stickers, identity cards, and the like to be printed on a special and extremely densely figured paper. Normally this paper itself is printed on its upper surface with the detailed figuring in such a manner that any attempt to erase or alter indicia printed on top of the thus-figured paper will eliminate the pattern and be highly visible. The disadvantage of this system is that the basic paper used is often very expensive. What is more it is possible for a skilled forger to redraw any damaged figuring, so that falsification is still possible.
It is also known to print the indicia on an extremely fragile foil. This is the procedure for approval stickers or the like which are then adhered by means of a strong pressure-sensitive adhesive to the vehicle, scale or other item. As the foil is very fragile, any attempt to lift it off one substrate and apply it to another will normally result in damaging of the foil. The disadvantage of this system is that it is still not impossible to lift the foil off and move it to another item. Furthermore it is occasionally possible merely to alter whatever indicia is on the foil without moving it. Finally another disadvantage is that this relatively fragile foil is frequently damaged during normal legitimate use of the item to which it is affixed.
It is also standard practice to make a so-called tamper proof identity card by laminating an indicia-bearing sheet between a pair of synthetic-resin sheets. Normally the two outer sheets are both transparent and of larger dimension than the indicia-bearing central sheet, and are secured to each other and to the respective opposite faces of the central sheet by means of a very strong bond, normally a pressure-sensitive adhesive or a thermally activated adhesive. This type of identity card has the disadvantage that a skilled forger can carefully peel off one or the other transparent sheets, so as to gain access to the sandwiched card and alter same.